Elemental Execution (Su)

At 4th level, a planar sneak treats creatures with the elemental subtype as though they were vulnerable to her sneak attack, but she deals only half as much sneak attack damage as she normally would. She can confirm critical hits against such creatures, though 50% of the time, the critical hit is automatically negated and damage is instead rolled normally. At 8th level, this ability also applies to all outsiders otherwise immune to critical hits and sneak attack damage.